Fluorosilicone rubber compositions, particularly those which are based on an organopolysiloxane polymer having a large proportion of fluoroalkyl, particularly perfluoroalkyl groups, when cured, possess properties rendering them resistant to heat, frost, chemicals, and exposure to oil. These compositions are therefore widely used in the automotive and aircraft industries. However, one major problem with cured fluorosilicone rubber is that it does not adhere well to other substrates such as other silicone rubber compositions.
Various methods have been proposed for improving adhesion of fluorosilicone rubbers to alternative silicone rubber based substrates and other substrate surfaces. These include the addition of materials containing multiple silicon-hydrogen bonds or multiple alkenyl groups in either the fluorosilicone rubber and/or other silicone rubber to enhance adhesion. The introduction of adhesion promoters such as cyanurate and/or isocyanurate based compounds for example triallyl cyanurate or triallyl isocyanurate in either the fluorosilicone rubber and /or other silicone rubber may also be used but can result in compatibility problems.
In US2008/0308227A, a method for the adhesion of a layer of fluorosilicone rubber which is curable using a non-hydrosilylation curing process to a layer of silicone rubber which contains substantially no perfluoroalkyl groups is disclosed. The method comprises the steps of:                i) incorporating either a hydrosilylation catalyst or a siloxane containing at least two silicon bonded hydrogen groups into the fluorosilicone rubber composition prior to curing and;        ii) incorporating the other of the hydrosilylation catalyst or the siloxane containing at least two silicon bonded hydrogen groups into the alternative silicone rubber composition prior to curing;        iii) forming the products of step (i) and step (ii) into required shapes;        iv) bringing the shaped products of step (iii) into contact with each other; and        v) adhering the shaped products in contact with each other together by effecting a hydrosilylation reaction therebetween.        